The invention pertains to ocular fixation aids for use by ophthalmologists, physicians and other medical personnel when examining and treating a patient's eyes, and particularly to ocular fixation aids that are effective to attract and maintain the patient's gaze and to stimulate accommodation (focusing of the eyes).
Ocular fixation aids are in general known and have been found especially useful when examining the eyes of infants and young children. Because infants and children have difficulty in following instructions and in maintaining visual concentration, such aids are used to display a small visually interesting object, called a target, to the patient that spontaneously attracts and thereafter holds the patient's gaze fixed on the object while the examination is carried out. An example of a known ocular fixation aid is disclosed in U.S. Pat. No. 3,484,155 issued to D. L. Prager et al.
However, known fixation aids have exhibited certain limitations which detract from their effectiveness. For example, the aid disclosed in U.S. Pat. No. 3,484,155 is mounted on a head strap worn by the person conducting the examination, and is thus not capable of being used concurrently with other types of head strap mounted instruments employed during ocular examinations. Furthermore, the fixation targets provided in U.S. Pat. No. 3,484,155 (two are disclosed) are inanimate, and as such, are not effective to maintain the patient's attention for more than brief periods. One target is a stationary toy figure. The other target is a toy figure supporting a small light connected to a blinking circuit that when turned on by a manually operated switch, blinks on and off at a constant rate. The constant repetition of the blinking light will soon result in disinterest of the patient. The repetition of the blinking light may be varied by turning the manually operated switch on and off however, such requires the use of one of the hands of the person conducting the examination, a hand that may be needed for holding another instrument or implement, such as an occluder.
It is therefore an object of the present invention to provide an entirely new approach to the design of such devices, an approach that is not subject to the foregoing limitations.
In particular it is an object of the present invention to provide an ocular fixation aid that can be held and oriented by the person conducting the examination in a way that does not interfere with the use of such person's hands for other purposes associated with the examination, and also does not interfere with the use of the various types of head mounted instruments that are available for assisting in the examination of eyes and treatment of ocular abnormalities.
Another object of the present invention is to provide an ocular fixation aid in which the target can be animated at will by the person conducting the examination so as to maintain the interest of the patient, and in which the animation of the target can be effected without requiring the use of such person's hands. A related object is to enable the person that is conducting the examination to control the timing of the target animation so that he can more readily observe accomodation of the patient's eyes as they focus on the movement of the target.
A further object of the present invention is to provide an ocular fixation aid that satisfies the above objectives and that is of relatively simple construction, that is readily mass produced at a low per unit cost, and that is durable and relatively small so that, for example, it can be carried in a physician's coat pocket, ready for use.